Exploring heat exchange in space: Recent advances in two-phase fluid experiments in microgravity

Thermal regulation has assumed a central role in space expeditions ever since the inception of Sputnik-1 in 1957. Throughout the years, numerous techniques have been developed to regulate temperatures in spacecraft and space habitats. Initially, passive systems like heat shields and thermal linings were employed, while newer missions embrace active cooling using fluids like ammonia and water. With significant advancements in lunar exploration, thermal management systems have been integrated to ensure effective heat protection and dissipation. Experiments carried out in drop towers, parabolic flights, sounding rockets, and aboard the International Space Station (ISS) have yielded valuable insights into the physics of fluids, pool boiling, boiling in two-phase flow, and cooling phenomena. However, conducting tests in microgravity conditions can lead to lower performances, and accurate numerical simulations remain a challenge. At present, various organizations are conducting research to drive progress in thermal management and enhance the technology of space devices. This review describes the most recent advances in two-phase fluid experiments in microgravity. Furthermore, the major challenges that persist in this field are presented and discussed, along with observations on trends and possibilities for the future of thermal control in space. This review attempts to be a relevant guide for future research and developments on thermal control in space.